Amenorrhea

Background

Menarche (the onset of menses) is an important milestone in female adolescent development, and is preceded by the onset of breast development (thelarche) and pubic hair (pubarche). Menses are often irregular at first, but ultimately normalize to a more regular cycle of 21-35 days, with 3 to 7 days of bleeding per cycle. This pattern continues throughout adult life until menopause.

Amenorrhea (the lack of menstruation) is a symptom, not a disease unto itself, and may be divided into primary (delayed menarche) or secondary amenorrhea (cessation of menses in someone who has previously menstruated). While some etiologies can cause both primary and secondary amenorrhea, they are distinct entities with subtly different diagnostic and etiologic frameworks.

Primary amenorrhea

The typical age of menarche varies somewhat between different countries and ethnic groups. In the United States, the typical age of menarche in healthy female adolescents is 12-13, with more than 80% achieving menarche between 11 and 14. Primary amenorrhea is traditionally defined as failure to achieve menarche by age 16. However, diagnostic evaluation is often initiated earlier, for the following indications, among others:

No menarche by age 15 (98% of females have undergone menarche by this age)

​ Most commonly functional hypothalamic amenorrhea: conditions such as chronic illness, chronic stress, excessive exercise, or very low BMI can impair the normal pulsatile release of GnRH from the hypothalamus

Secondary Amenorrhea

Secondary amenorrhea is typically defined as the absence of menses for a consecutive period of 3 cycles or 6 months in a woman who has previously menstruated. Although irregular menstruation is quite common in the first year or two following menarche, the absence of menstruation for more than 3 consecutive cycles merits further investigation even among this group.

The diagnostic evaluation of secondary amenorrhea is very similar to that for primary amenorrhea, with enhanced focus on the sexual history including contraceptive practices and sexually transmitted infections, as well as a detailed menstrual history. Previous gynecologic surgeries or procedures are also an important consideration since endometrial scarring and intrauterine synechiae may result (Asherman syndrome).

It is critical to remember that the most common cause of secondary amenorrhea is pregnancy!A pregnancy test should always be included in the workup of secondary amenorrhea, regardless of reported history.